The present invention relates initially, and thus generally, to an improved vacuum cleaner. More specifically, the present invention relates to an improved vacuum cleaner that utilizes a toroidal vortex such that the air pressure within the device housing is below atmospheric. In the present invention, this prevents dust-laden air within the device from being carried to the surrounding atmosphere.
The use of vortex forces is known in various arts, including the separation of matter from liquid and gas effluent flow streams, the removal of contaminated air from a region and the propulsion of objects. However, a toroidal vortex has not previously been provided in a bagless vacuum device having light weight and high efficiency.
The prior art is strikingly devoid of references dealing with toroidal vortices in a vacuum cleaner application. However, an Australian reference has some similarities. Though it does not approach the scope of the present invention, it is worth disusing its key features of operation such that one skilled in the art can readily see how its shortcomings are overcome by the present invention disclosed herein.
In discussing Day International Publication number WO 00/19881 (the Day publication), an explanation of the Coanda effect is required. This is the ability for a jet of air to follow around a curved surface. It is generally referred to without explaining the effect, but is simply understood provided that one makes use of xe2x80x9cmomentumxe2x80x9d theory; a system based on Newton""s laws of motion, rather than try to weave an understanding from Bernoulli.
FIG. 1 shows the establishment of the Coanda effect. In (A) air is blown out horizontally from a nozzle 100 with constant speed V. The nozzle 100 is placed adjacent to a curved surface 102. Where the air jet 101 touches the curved surface 102 at point 103, the air between the jet 101 and the surface 102 as it curves away is pulled into the moving airstream both by air friction and the reduced air pressure in the jet stream, which can be derived using Bernoulli. As the air is carried away, the pressure at point 103 drops. There is now a pressure difference across the jet stream so the stream is forced to bend down, as in (B). The contact point 104 has moved to the right. As air is continuously being pulled away at point 104, the jet continues to be pulled down to the curved surface 102. The process continues as in (C) until the air jet velocity V is reduced by air and surface friction.
FIG. 2 shows the steady state Coanda effect dynamics. Air is ejected horizontally from a nozzle 200 with speed represented by vector 201 tangentially to a curved surface 203. The air follows the surface 203 with a mean radius 204. Air, having mass, tries to move in a straight line in conformance with the law of conservation of momentum. However, it is deflected around by a pressure difference across the flow 202. The pressure on the outside is atmospheric, and that on the inside of the airstream at the curved surface is atmospheric minus xcfx81V2/R where xcfx81 is the density of the air.
The vacuum cleaner coanda application of the Day publication has an annular jet 300 with a spherical surface 301, as shown in FIG. 3. The air may be ejected sideways radially, or may have a spin to it as shown with both radial and tangential components of velocity. Such an arrangement has many applications and is the basis for various xe2x80x9cflying saucerxe2x80x9d designs.
The simplest coanda nozzle 402 described in the Day publication is shown in FIG. 4. Generally, the nozzle 402 comprises a forward housing 407, rear housing 408 and central divider 403. Air is delivered by a fan to an air delivery duct 400 and led 401 to an output nozzle 402. At this point the airflow cross section is reduced so that air flowing through the nozzle 402 does so at high speed. The air may also have a rotational component, as there is no provision for straightening the airflow after it leaves the air pumping fan. The central divider 403 swells out in the terminating region of the output nozzle 402 and has a smoothly curved surface 404 for the air to flow around into the air return duct using the coanda effect.
Air in the space below the coanda surface moves at high speed and is at a lower than ambient pressure. Thus dust in the region is swept up 405 into the airflow 409 and carried into the air return duct 406. For dust to be carried up from the surface, the pressure is preferably low and carrying the air up the return duct 406, requires a steady airflow. After passing through a dust collection system the air is connected through a fan back to the air delivery duct. Constriction of the airflow by the output nozzle leads to a pressure above ambient in this duct ahead of the jet. In sum, air pressure within the system is above ambient in the air delivery duct and below ambient in the air return duct. The overall system is not shown, as this is not necessary to understand its fundamental characteristics.
Coanda attraction to a curved surface is not perfect, and as shown in FIG. 5, not all the air issuing from the output nozzle is turned around to enter the air return duct. An outer layer of air proceeds in a straight fashion 501. When the nozzle is close to the floor, this stray air will be deflected to move horizontally parallel to the floor and should be picked up by the air return duct if the pressure there is sufficiently low. In this case, the system may be considered sealed; no air enters or leaves, and all the air leaving the output nozzle is returned.
When the nozzle is high above the ground, however, there is nothing to turn stray air 501 around into the air return duct and it proceeds out of the nozzle area. Outside air 502, with a low energy level is sucked into the air return to make up the loss. The system is no longer sealed. An example of what happens then is that dust underneath and ahead of the nozzle is blown away. In a bagless system such as this, where fine dust is not completely spun out of the airflow but recirculates around the coanda nozzle, some of this dust will be returned to the surrounding air.
Air leakage is exacerbated by rotation in the air delivery duct caused by the pumping fan. Air leaving the output nozzle rotates so that centrifugal force spreads out the airflow into a cone. The results in the generation of a larger amount of stray air. Air rotation can be eliminated by adding flow straightening vanes to the air delivery duct, but these are neither mentioned nor illustrated in the Day publication.
A side and bottom view of an annular coanda nozzle 600 is shown in FIG. 6. This is a symmetrical version of the nozzle shown in FIG. 4. Generally, the nozzle 600 comprises outer housing 602, air delivery duct 601, air return duct 605, flow spreader 603 and annular coanda nozzle 604. Air passes down though the central air delivery duct 601, and is guided out sideways by a flow spreader 603 to flow over an annular curved surface 604 by the coanda effect, and is collected through the air return duct 605 by a tubular outer housing 602.
This arrangement exhibits similar behavior as previously described. Air strays away from the coanda flow, particularly when the jet is spaced away from a surface.
While it is conceivable that the performance of the invention of the Day publication would be improved by blowing air in the reverse direction, down the outer air return duct and back up through the central air delivery duct, stray air would then accumulate in the central area rather than be ejected out radially. Unfortunately, the spinning air from the air pump fan would cause the air from the nozzle to be thrown out radially due to centrifugal force (centripetal acceleration) and the system would not work. This effect could be overcome by the addition of flow straightening vanes following the fan. However, the Day publication does not disclose a means for staightening airflow.
The Day publication has more complex systems with jets to accelerate airflow to pull it around the coanda surface, and additional jets to blow air down to stir up dust and others to optimize airflow within the system. However, these additions are not pertinent to the analysis herein.
The new toroidal vortex vacuum cleaner is a bagless design and one in which airflow must be contained within itself at all times. Air continually circulates from the area being cleaned, through the dust collector and back again. Dust collection is not perfect and so air returning to the surface is dust laden. This air must, of course, contact the surface in order to pick up more dust but must not be allowed to escape into the surrounding atmosphere. It is not sufficient to design the cleaner to ensure essentially sealed operation while operating adjacent to a surface being cleaned, it must also remain sealed when away from a surface to prevent fine dust particles from re-entering the surrounding air.
Another reason for maintaining sealed operation when away from the surface is to prevent the vacuum cleaner nozzle from blowing surface dust around when it is held at a distance from the surface.
The Day publication, in most of its configurations, is coaxial in that air is blown out from a central duct and is returned into a coaxial return duct. The toroidal vortex attractor is coaxial and operates the reverse way in that air is blown out of an annular duct and returned into a central duct. The one is the reverse of the other.
The inventor has also noted the presence of cyclone bagless vacuum cleaners in the prior art. The present invention utilizes an entirely different type of flow geometry allowing for much greater efficiency and lighter weight. Nonetheless, the following represent references that the inventor believes to be representative of the art in the field of bagless cyclone vacuum cleaners. One skilled in the art will plainly see that these do not approach the scope of the present invention.
Dyson U.S. Patent No. 4,593,429 discloses a vacuum cleaning appliance utilizing series connected cyclones. The appliance utilizes a high-efficiency cyclone in series with a low-efficiency cyclone. This is done in order to effectively collect both large and small particles. In conventional cyclone vacuum cleaners, large particles are carried by a high-efficiency cyclone, thereby reducing efficiency and increasing noise. Therefore, Dyson teaches incorporating a low-efficiency cyclone to handle the large particles. Small particles continue to be handled by the high-efficiency cyclone. While Dyson does utilize a bagless configuration, the type of flow geometry is entirely different. Furthermore, the energy required to sustain this flow is much greater than that of the present invention.
Song, et al U.S. Pat. No. 6,195,835 is directed to a vacuum cleaner having a cyclone dust collecting device for separating and collecting dust and dirt of a comparatively large particle size. The dust and dirt is sucked into the cleaner by centrifugal force. The cyclone dust collecting device is biaxially placed against the extension pipe of the cleaner and includes a cyclone body having two tubes connected to the extension pipe and a dirt collecting tub connected to the cyclone body. Specifically, the dirt collecting tub is removable. The cyclone body has an air inlet and an air outlet. The dirt-containing air sucked via the suction opening enters via the air inlet in a slanting direction against the cyclone body, thereby producing a whirlpool air current inside of the cyclone body. The dirt contained in the air is separated from the air by centrifugal force and is collected at the dirt collecting tub. A dirt separating grill having a plurality of holes is formed at the air outlet of the cyclone body to prevent the dust from flowing backward via the air outlet together with the air. Thus, the dirt sucked in by the device is primarily collected by the cyclone dust connecting device, thus extending the period of time before replacing the paper filter. The device of Song et al differs primarily from the present invention in that it requires a filter. The present invention utilizes such an efficient flow geometry that the need for a filter is eliminated. Furthermore, the conventional cyclone flow of Song et al is traditionally less energy efficient and noisier than the present invention.
Thus, there is a clear and long felt need in the art for a light weight, efficient and quiet bagless vacuum cleaner.
The present invention was developed from the applicant""s prior inventions regarding toroidal vortex attractors.
Described herein are embodiments that deal with both toroidal vortex vacuum cleaner nozzles and systems. The nozzles include simple concentric systems and more advanced, optimized systems. Such optimized systems utilize a thickened inner tube that is rounded off at the bottom for smooth airflow from the air delivery duct to the air return duct. It is also contemplated that the nozzle include flow straightening vanes to eliminate rotational components in the airflow that would greatly harm efficiency. The cross section of the nozzle need not be circular, in fact, a rectangular embodiment is disclosed therein, and other embodiments are possible.
A complete toroidal vortex bagless vacuum cleaner is also disclosed. The air mover is a centrifugal pump, much like those used in certain toroidal vortex attractor embodiments. Air leaving the centrifugal pump blades is spinning rapidly so that dust and dirt are thrown to the sidewalls of the casing. Ultimately, dirt is deposited in a centrifugal dirt separation area. The air then turns upwards over a dirt barrier and down the air delivery duct. At this point, the air is quite clean except for the finest particulates that do not deposit in the centrifugal dirt separation area. These particulates circulate through the system repeatedly until they are eventually deposited. The system operates below atmospheric pressure so that air laden with fine dust is constrained within the system, and cannot escape into the surrounding atmosphere.
Unlike other vacuum cleaners that employ centrifugal dust separation (e.g., the xe2x80x9ccyclonexe2x80x9d types discussed above), the present invention spins the air around at the blade speed of the centrifugal pump. Thus, the system acts like a high speed centrifuge capable of removing very small particles from the airflow. Therefore, no vacuum bag or HEPA filter is required.
One of the main features of the present invention is the inherent low power consumption. There are no losses that must exist when bags or HEPA filters are utilized. These devices restrict the airflow, thus requiring greater power to maintain a proper flow rate. The majority of the power saving, however, comes from the closed air system in which energy supplied by the pump is not lost as air is expelled into the atmosphere, but is retained in the system. The design is expected to be practically maintenance free.
Thus, it is an object of the present invention to utilize toroidal vortices in a vacuum cleaner application.
It is a further object of the present invention to provide toroidal vortex vacuum cleaner nozzles.
It is yet another object of the present invention to provide a complete toroidal vortex vacuum cleaner system.
Additionally, it is an object of the present invention to provide an efficient vacuum cleaner.
Furthermore, it is an object of the present invention to provide a quiet vacuum cleaner.
It is a further object of the present invention to provide a light weight vacuum cleaner.
In addition, it is an object of the present invention to provide a low-maintenance vacuum cleaner.
It is yet another object of the present invention to provide a bagless vacuum cleaner.
It is a further object of the present invention to provide a vacuum cleaner that does not require the use of filters.